Apparatus for cooling a moving bed of solid, gas permeable particles

ABSTRACT

Apparatus is provided for efficiently cooling a moving bed of gas permeable particles descending downwardly through a converging bin. The apparatus includes a support mechanism and an especially configured gas distributor depending downwardly therefrom within the bin. The distributor includes a plurality of tiered gas units in nested relationship with one another and arranged in progressively smaller sizes from the top of the distributor. Each gas unit contains a predetermined number of peripherally spaced gas outlet ports to provide streams of cooling gas under sufficient pressure at each unit to effectively cool the bed of particles.

I451 Sept. 17, 1974 United States Patent [1 1 Beggs APPARATUS FORCOOLING A MOVING BED OF SOLID, GAS PERMEABLE PARTICLES PrimaryExaminerGerald A. Dost Attorney, Agent, or Firm-Morgan, Finnegan, Durham& Pine [75] Inventor: Donald Beggs, Toledo, Ohio [57] ABSTRACT Apparatusis provided for efficiently cooling a moving [73] Assignee: MildrexCorporation, Toledo, Ohio [22] Filed: Dec. 26, 1973 bed of gas permeableparticles descending downwardly through a converging bin. The apparatusin- [21] Appl. No.: 428,146

cludes a support mechanism and an especially configured gas distributordepending downwardly therefrom within the bin. The distributor includesa plurality of tiered gas units in nested relationship with one anotherand arranged in progressively smaller sizes from the top of thedistributor. Each gas unit contains a predetermined number ofperipherally spaced gas outlet ports to provide streams of cooling gasunder sufficient pressure at each unit to effectively cool the bed ofparticles.

[56] References Cited UNITED STATES PATENTS DeVaney 266/20 Beggs et266/29 5 Claims, 3 Drawing Figures PAIENIEnsm mm mm 1 0r 2 Ill SCRUB ANDCOOL APPARATUS FOR COOLING A MOVING BED OF SOLID, GAS PERMEABLEPARTICLES This invention relates generally to an apparatus for coolinggas pervious particles and more particularly to apparatus for coolingabed of such particles flowing downwardly through a converging bin.

The invention is particularly applicable to vertical shaft-type furnaceswhich directly reduce iron oxideto metallic iron and employ a coolingleg at the lower portion thereof to cool the metallic particles and willthus be described with particular reference thereto. However, it will beappreciated by those skilled in the art that the invention has broaderapplications and may be applied as a means for cooling any moving bed ofgas permeable solid particles.

Vertical shaft furnaces employing counterflow gas principles have beenfound to be especially suited for heat treatment of pelletized, sized orlump iron ore whether the ore is to be indurated into oxide pellets inan oxide furnace or directly reduced from oxide pellets into metalliciron in a reduction furnace. With both types of furnace it is desirableto cool the pellets before discharging same into the atmosphere. Coolingis especially critical in a direct reduction furnace because themetallic iron (Fe) is in a very active state at its relatively highreduction temperature, typically l,300l ,500F. If the metallic ironpellets are not thoroughly cooled to nominally 125F., the pellets tendto become critically pyrophoric in nature when exposed to air at ambienttemperature.

To alleviate this tendency, several cooling arrangements have beenemployed in the cooling leg portion of such furnaces. Such cooling legportions may be viewed as discharge bins which converge into a throatsection to assure an accurate pellet descent rate through the furnace.One known arrangement simply comprised an upright, hollow cone andcooling gas was directed into the interior thereof. Such arrangementproved generally unsatisfactory because the cooling gas simply could notpermeate a sufficent amount of pellets within the bed to adequately coolthe bed. Another possible attempt directed at providing sufficientquantities of cooling gas to the bed consisted of applying a number ofcooling gas pipes in axially spaced arrangement through the wall of theconverging bin. Such arrangements are unsatisfactory because the fastestmoving particles at the center of the bin did not receive sufficientamounts of cooling gas which was primarily directed at the slowestmoving particles adjacent the converging walls of the bin. In an attemptto overcome such difficulties, it has been known to employ a gasdistributor extending downwardly in a converging configuration into thebin and having at axially spaced locations theralong discharge portsthrough which cooling gas is introduced into the bed. While suchapparatus did improve cooling because the cooling gas was introducedadjacent the fastest moving portion of the bed at several locations, thedesign of the mechanism was such that most of the cooling gas exited atthe upper ports of the distributor which correspondingly diminished theeffectiveness of the cooling gas at the lower portions of thedistributor.

It is thus an object of the subject invention to provide apparatus forcooling a downwardly flowing bed of gas permeable particles in aconverging bin by introducing streams of cooling gas adjacent thefastest flowing areas of particles within the bed to provide improvedutilization of the cooling gas.

This object along with other features of the subject invention isachieved by providing an especially configured gas distributor within aconverging bin through which a bed of solid, gas permeable particlesdescends. The gas distributor extends downwardly in a convergingconfiguration within the bed and includes a predetermined plurality ofgas discharge ports peripherally spaced about the distributor in arrayswhich are axially spaced along the length thereof. The number of portsand correspondingly the net discharge area associated with each array issized as a function of 'the array position within the bed to assure, atthe least, approximately equal discharge rates of the cooling gas fromeach discharge port array. This configuration assures that the fastestmoving particles at the center of the descending bed are subjected toseveral streams of cooling gas as they descend past the distributor toassureef- ,fective cooling of the entire bed.

In accordance with another feature of the subject invention, theconverging configuration of the gas distributor comprises a plurality ofsuccessively smaller sized tiered gas units, one nested within theother. Each unit comprises a continiuous side wall having a top end atwhich is formed an outwardly extending support flange. The supportflange of any given unit is positioned at a given distance within theside wall of the next larger unit immediately thereabove. Thus thebottom end of the side wall of each gas unit comprises a leading edge todefine an overhanging lip which surrounds the upper side wall portion ofthe smaller unit positioned directly below. This leading edge preventsparticles from flowing into the gas discharge ports which are spacedclosely adjacent the top end of each side wall. In the event thatparticles do enter the gas distributor, blockage is prevented by an exitprovided as an opening in the end wall of the smallest gas unitat thebottom of the distributor. This opening adds to the net discharge areaof that gas unit, as such discharge area, without the opening in the endwall, may not be sufficient to establish an adequate stream of coolinggas flow therethrough because of the small size of that unit.

It is thus another object of the subject invention to provide anapparatus for cooling a downwardly flowing bed of gas permeableparticles by a plurality of axially spaced discharge gas ports which areshielded in a manner to prevent blockage thereof.

The invention may take physical form in certain parts and arrangement ofparts, a preferred embodiment of which will be described in detailherein and illustrated in the accompanying drawings which form a parthereof and wherein:

FIG. 1 is an elevated view, in section, of a vertical shaft furnaceemploying the cooling apparatus of the subject invention;

FIG. 2 is a larger elevation view, in section, of the cooling apparatusshown in FIG. 1; and

FIG. 3 is a cross-sectional view of the cooling apparatus taken alongline 33 of FIG. 2.

Referring now to the drawings wherein the showings are for the purposeof illustrating a preferred embodiment of the invention only and not forthe purpose of limiting same, there is shown in FIG. 1 a refractorylined, vertical shaft furnace 10 having a cooling leg section 12 at thebottom thereof and cooling apparatus 13 disposed within cooling leg 12for cooling a descending bed of gas permeable solid particles 14, hereindefined as iron oxide pellets, lumps or sized ore.

Shaft furnace is equipped with a feed hopper 16 at the top thereof whichis fed pellets from a source 18. A pellet feed pipe 20 supplies thepellets to the reduction furnace 10 wherein a first stockline 11 isestablished by the angle of repose of the pellets within the furnace.The bottom of furnace 10 is defined by a throat section 22 which entersinto the cooling leg section 12. Spaced above throat section 22 is abustle and tuyere arrangement 25 which receives hot reducing gas, shownas arrows 26, from a gas inlet pipe 28 which in turn is connnected to asource of reducing gas 29. Reducing gas is introduced radially inwardlyinto the shaft furnace by a series of wall ports 30 in the bustle andtuyere arrangement 25 and the reducing gas flows vertically upward incounterflow relationship to the descending bed 14. The reacted reducinggas exits from bed 14 at stockline 21 and thence through an off-takepipe 32.

Hot pellets, now reduced into metallic iron by the reducing gas, flowdownwardly into cooling leg section 12 through throat 22 to establish asecond stockline 33 within cooling leg 12. Cooling leg 12 may beproperly viewed as a discharge bin formed in part by an external wallclosed about a predetermined periphery to define a covergingconfiguration. This converging configuration is shown herein as afrusto-conical wall portion 35 which is disposed between a circularthroat portion 36 at the bottom of the cooling leg and a larger circularwall portion 37 which defines a pellet retaining area at the top of thecooling leg. The gravitational rate of descent of the bed 14 of pelletswithin cooling leg 12, furnace 10 and feed hopper 16 is controlled by asuitable belt feeder assembly 38 positioned below cooling leg throat 36and driven by a motor 39.

Cooling apparatus 13 within cooling leg 12 generally comprises a supportmechanism 40 extending through and supported by frusto-conical wall 35and in turn supporting a gas distributor 42 depending downwardlytherefrom and centered on vertical centerline 43 of frusto-conical wall35 which coincides with the centerline of cooling leg 12 anf furnace 10.A pressurized cooling gas indicated by arrows 45 is directed fromdistributor 42 into bed 14 in a manner to be explained hereafter andleaves the bed at stockline 33 whereupon it exits from the cooling legas a relatively hot gas through off-take pipe 46 adjacent stockline 33.The heated or spent cooling gas is then cleansed and cooled in asuitable cooler-scrubber 47 and pressurized in a compressor 49 beforebeing introduced into the cooling apparatus 13 to define a closed loopcooling circuit.

Referring now to FIGS. 2 and 3, support mechanism 40 is shown tocomprise a bustle 50 circumferentially extending about frusto-conicalwall portion 35 and a central discharge unit 52 positioned at thegeometric center of bustle 50. Central discharge unit 52 is supported byfour diamond shaped feed pipes 53 which are spaced 90 apart from oneanother and extend radially inwardly towards the center of bustle 50 andthrough frusto-conical wall portion 35 which in turn supports the entiresupport mechanism 40. As best seen in FIG. 2, central discharge unit isdefined by a frusto-conical side wall 55 which is open at its bottom end56 and closed at its top end by a top wall 57. Cooling gas enters bustle50 through suitable connections (not shown) and exits from the bustlethrough feed pipes 53 into central discharge unit 52 and exits from thebottom thereof into gas distributor 42.

Generally described, gas distributor 42 extends downwardly into coolingleg 12 in a coverging configuration characterized by a predeterminednumber of peripherally spaced gas discharge ports 60 arranged in axiallyspaced arrays 61 along the. distributor length. More particularly, eachport array 61 is contained within a gas discharge unit 63. Eachdischarge port 60 is shown herein to be equally sized and the number ofports which constitutes a given arry 61 defines a net discharge area forthat array. It is desirable for optimum cooling results that the netdischarge area progressively increase for arrays progressively spacedfrom the top of gas distributor 42. As a matter of practice, the size ofgas distributor 42 may limit the net discharge area of the lowest arraysin which case it is desirable to maintain the area of such arrays asnearly equal to that of the higher arrays as possible.

Structurally, gas discharge units 63, and specifically identified as 63ato 63f with corresponding parts identified by like subscripts whereapplicable, are nested one within another and extend in a tieredarrangement which becomes progressively smaller in size from the topunit 63a to the bottom gas unit 63f. Each gas unit 63 is shown tocomprise a peripherally extending open ended sidewall 67. At the top ofeach side wall an outwardly extending support flange 68 is formed. Eachsupport flange 68 of each gas unit 63 is positioned within and securedto the side wall 67 of that gas unit immediately thereabove. The sidewall 67 of each gas unit thus extends below the support flange 68 of thenext lower unit to define an overhanging lip 69 which circumscribes andshrouds the top portion of the side wall 67 of each gas unit. Eachoverhanging lip 69 thus forms a stockline 70 at eachlgas unit 63 toprevent pellets from clogging distributor 42 by entering outlet ports 60which importantly are spaced adjacent the top end of each gas outletside wall 67 and thus shrouded by overhanging lip 69. In the event thatsome pellets do enter distributor 42, an exit path through thedistributor is provided by an opening 72 in an end wall 73 at the bottomof the side wall of the smallest gas unit 63f. Opening 72 is included inthe net discharge area for gas unit 63f. Distributor 42 is similarlyconnected to central discharge unit 52 of support mechanism 40 by thesupport flange 68a of the largest gas unit, being nested withinfrusto-conical side wall 55 in a manner similar to which the other gasunits 63 are connected to one another.

As thus described, streams of cooling gas will exit from each gas outletunit 63 to effectively cool the bed 14 of pellets as it passesdownwardly by distributor 42. Cooling of the bed occurs becausedistributor 42 is optimized in design in accordance with geometricconsiderations involved in passing a moving bed of pellets through aconverging area. That is known flow considerations of the pelletsestablish that the pellets within the bed at the centerline 43 of thecooling leg or bin 12 will be traveling the fastest of all the pelletswithin the bed, the pellets adjacent exterior frusto-conical wall 35will have the slowest velocity of the pellets within the bed, and avelocity gradient will occur across the bed by which the speed of theother pellets can be determined accordingly. Because distributor 42introduces the cooling gas adjacent the fastest moving pellets withinthe bed, sucy pellets are initially impinged by the gas while high incooling quality. As the cooling gas permeates radially-outwardly throughthe bed, it loses its high cooling quality but the slower moving pelletsare exposed to the cooling gas for a longer period of 5 time toaccordingly compensate for this loss.

It has been found, especially in cooling leg sections of shaft furnaceswhich directly reduce iron ore into metallic iron, that the introductionof only one stream of cooling gas into the cooling leg section 12 willnot sufficiently cool the pellets passing through the cooling leg.Furthermore, it was found that providing a plurality of discharge portsat axially spaced locations along the length of the distributor did notresult in optimum cooling of the bed because of static head pressureconditions within the bed. That is, the pressure gradient betweenstockline 33 and point of discharge into the cooling stream is a minimumat the uppermost gas unit 63a and a disproportionate amount of coolinggas thus tends to exit from the uppermost gas unit which alsoestablishes the shortest flow path through the bed. In accordance withthe subject invention, the pressure gradient in effect is neutralizedthroughout the bed by the number of gas discharge ports 60 providedwithin each array 61 in distributor 42. More particularly, it has beenfound that if the net area of all discharge ports for each gas unit wereat least made equal and preferably progressively larger for the smallergas units, sufficient quantities of cooling gas would be supplied ateach gas unit to effectively cool the bed of pellets as same passes bydistributor 42. The distributor 42 is thus characterized as beingpositioned along its entire length closely adjacent to the fastestmoving particles within the descending bed and having pluralities ofperipherally spaced discharge ports 60 arranged in axially spaced arrays62 with each array having a net discharge area defined by its portswhich is sized with respect to the other array areas to producesufficient quantities of gas leaving each array for effective cooling ofthe particle bed.

The invention has been described with reference to a preferredembodiment. Obviously, modifications and alterations will occur toothers, upon reading and understanding the specification. It is myintention to include all such modifications and alterations insofar asthey come within the scope of the present invention.

The cooling mechanism has been shown applied to the cooling leg sectionof a shaft furnace for illustrative purposes only. It should be clearfrom the above description that the cooling mechanism may be applied toany moving bed of gas permeable solid particles heated by means otherthan a shaft furnace.

It is thus the essence of the subject invention to provide in aconverging discharge bin through which a moving bed of particles pass, acooling apparatus which utilizes a plurality of discharge areas sized inrelation to one another to assure a plurality of effective cooling gasstreams exiting therefrom to efficiently cool the moving bed ofparticles in the discharge bin. Having thus defined my invention, 1claim: 1. Apparatus for cooling a gas permeable bed of descending solidparticles comprising:

an axially-extending wall portion, closed about a predeterminedperiphery to define a hollow body converging towards its bottom end;means for introducing said particles into said body and withdrawing samefrom the bottom thereof; cooling means within said body for introducinga cooling gas under pressure in counterflow relationship to saiddescending bed, said cooling means including: a. support means extendingwithin said wall portion and carrying said cooling gas, and b. a gasdistributor secured to said support means and receiving said cooling gastherefrom, said distributor extending in a converging configurationdownwardly into said body and having a predetermined number ofperipherally spaced gas discharge ports arranged in axially spacedarrays along its length whereby said distributor introduces said coolinggas to said particles at predetermined flows along its length. 2. Theapparatus according to claim 1 wherein: the total area of said dischargeports in any given array is sized as a function of bed pressure adjacentsaid given array. 3. Apparatus according to claim 2 wherein: saiddownwardly extending converging configuration of said distributor isdefined by a plurality of successively smaller sized tiered gasdischarge units, each discharge unit nested within an adjacent gas unitspaced vertically thereabove and each unit containing an array of saidpredetermined number of peripherally spaced gas discharge ports. 4. Theapparatus of claim 3 wherein: each gas unit includes a side wall havinga top and bottom end, a support flange extending outwardly from said topend and said plurality of discharge ports positioned adjacent said topend; and said support flange of each unit positioned within said sidewall of an adjacent unit, each side wall of each unit extendingdownwardly beyond each support flange of an adjacent unit thuspositioned to define an overhanging lip shrouding said ports of a gasunit immediately therebelow. 5. The apparatus of claim 4 wherein: thesmallest in size gas unit has an end wall extending from said bottom ofsaid side wall thereof, said bottom wall having a gas discharge portextending therethrough.

1. Apparatus for cooling a gas permeable bed of descending solidparticles comprising: an axially-extending wall portion, closed about apredetermined periphery to define a hollow body converging towards itsbottom end; means for introducing said particles into said body andwithdrawing same from the bottom thereof; cooling means within said bodyfor introducing a cooling gas under pressure in counterflow relationshipto said descending bed, said cooling means including: a. support meansextending within said wall portion and carrying said cooling gas, and b.a gas distributor secured to said support means and receiving saidcooling gas therefrom, said distributor extending in a convergingconfiguration downwardly into said body and having a predeterminednumber of peripherally spaced gas discharge ports arranged in axiallyspaced arrays along its length whereby said distributor introduces saidcooling gas to said particles at predetermined flows along its length.2. The apparatus according to claim 1 wherein: the total area of saiddischarge ports in any given array is sized as a function of bedpressure adjacent said given array.
 3. Apparatus according to claim 2wherein: said downwardly extending converging configuration of saiddistributor is defined by a plurality of successively smaller sizedtiered gas discharge units, each discharge unit nested within anadjacent gas unit spaced vertically thereabove and each unit containingan array of said predetermined number of peripherally spaced gasdischarge ports.
 4. The apparatus of claim 3 wherein: each gas unitincludes a side waLl having a top and bottom end, a support flangeextending outwardly from said top end and said plurality of dischargeports positioned adjacent said top end; and said support flange of eachunit positioned within said side wall of an adjacent unit, each sidewall of each unit extending downwardly beyond each support flange of anadjacent unit thus positioned to define an overhanging lip shroudingsaid ports of a gas unit immediately therebelow.
 5. The apparatus ofclaim 4 wherein: the smallest in size gas unit has an end wall extendingfrom said bottom of said side wall thereof, said bottom wall having agas discharge port extending therethrough.